I was a little confused by their assertion that a big spaceship would be unlikely to have a crew aboard. Accelerating a big thing aggressively takes a lot of oomph (I believe the scientific term is DeltaV).
To use a modern example a racing power boat would leave a nuclear powered aircraft carrier in it’s wake in a drag race from a standing start. But the aircraft carrier has it in the bag if you’re circumnavigating the globe.
The big spaceship may be capable of travelling very fast, but it’s the acceleration that pastes you over the aft bulkhead.

I think the issue is that the whole idea of large, crewed spaceships is unworkable. Most of the bulk of the ship comes from keeping the crew alive, and in the real world the tasks we do in space don’t need a crew at all, so why spend all that energy moving all that mass around? It’s the debate about how realistic manned spaceflight is at all.

That assumes that a big spaceship needs a big crew (I accept that historically warships have had large crews compared to civilian ships of similar displacement). In the overlap between the Age of Sail and the Age of Steam, the Windjammers were built to have what was considered a tiny crew for what were amongst the largest sailing ships ever built.

If you use the tractor/trailer configuration (Nostromo) then the trailer doesn’t need any life support at all, and the tractor only has to maintain half a dozen grease monkey’s (or highly qualified reactor engineers more likely).

The real bulk problem is carrying enough reaction mass to get up to speed and then slow down again.